<!DOCTYPE html>
<html><head>
<style>
#outer {
    opacity: 0.8;
    background-color:red;
    width: 200px;
}

#inner {
    opacity: 0.6;
    background-color:white;
    color:white;
}

</style>
</head>
<body>
  <div id="outer">
    <div style="width:200px; height:200px; background:black;"></div>
    <div id="inner">
      <div style="width:200px; height:200px; background:black;"></div>
      <div style="width:200px; height:200px; background:rgb(50,50,50);"></div>
    </div>
  </div>
</body></html>

